Urinary incontinence (UI) is the involuntary leakage of urine. There are several types of urinary incontinence, including urge urinary incontinence (UUI) and stress urinary incontinence (SUI). Urge urinary incontinence is the involuntary loss of urine while suddenly feeling the need or urge to urinate. Stress urinary incontinence, typically affecting females, is the involuntary loss of urine resulting from increased abdominal pressure, such as generated by physical activity, exercising, coughing, sneezing, laughing, lifting, etc. Mixed incontinence combines attributes of SUI and UUI.
Overactive bladder (OAB) is the strong, sudden urge to urinate, with or without urinary incontinence, usually with frequency and nocturia. The urge associated with overactive bladder can be assessed using the subjective experience of the patient, with or without any objectively verifiable metric, condition, behavior, or phenomena.
Historically, attempts have been made to translate the subjective patient experience of overactive bladder into a verifiable clinical test. Based upon work in spinal cord injury patients, it was hypothesized that the sensation of urgency and the result of urine leakage was due to non-volitional urinary bladder detrusor muscle contractions. Consequently, there was a push to implement urodynamic testing to observe and quantify the presumed detrusor contractions. However, the results found a poor correlation (e.g., 60%) between observed detrusor overactivity and the experience of urgency, and also found that asymptomatic individuals may exhibit detrusor contractions during urodynamic testing.
Given the limitations of urodynamic testing, the diagnosis and treatment decisions for overactive bladder transitioned to being assessed wholly by the patient's subjective experience. However, the detrusor muscle and its contractions are still considered to have a major role in overactive bladder.
Bladder control is a complex combination of voluntary and involuntary neurologic control, which responds to a highly distributed set of afferent (sensory) nerves associated with the bladder. Also, there is evidence of a myogenic origin for at least a portion of bladder wall contractile activity. While there are some descriptive hallmarks of idiopathic overactive bladder (e.g., thickened wall, characteristic “patchy” denervation, changes in smooth muscle and collagen morphology, increased electrical connectivity), there is no specific anatomic cause of OAB (e.g., a lesion, defect, injury, etc.), and also it is believed that there is no commensurate remedy for the cause. Neurogenic injury (e.g., spinal cord injury) and bladder outlet obstruction (BOO) can both lead to overactive bladder due to a chronic state of bladder inflation and a “high pressure” bladder. However, resolution of an outlet obstruction fails to rectify overactive bladder symptoms in a significant fraction (e.g., 25%) of these patients.
Overactive bladder affects at least 33 million patients in the United States alone, representing 16% of the adult United States population and roughly $12 billion dollars in healthcare cost. Overactive bladder and urinary incontinence significantly affect the quality of life and the ability of patients to maintain their lifestyle, including socializing, mobility, or independence. Further, urinary incontinence is one of the most common reasons for entering long-term care facilities, such as nursing homes, and is also a significant risk factor for injury due to falls resulting from hurrying to the toilet in response to urge.
Referring to FIGS. 1-3, the anatomy of the female bladder is described to provide context for discussion of previously-known treatment modalities, and is illustrative of why a significant unmet need for improved treatment modalities remains. In particular, FIG. 1 depicts a lateral sectional of the anatomical structures of a bladder (B) and a urethra (U), while FIG. 2 depicts an anterior sectional view of the bladder and urethra. FIGS. 1-2 further illustrate a trigone (T), ureteral ostium (O) (also referred to as a ureteral orifice), detrusor muscle (D), a neck (N), an interureteric crest (C), a fundus (F), and a body (BB).
FIG. 3 depicts a cross sectional view of a wall of the bladder, including an intravesical region (IR) (also referred to as the cavity), mucous membrane (also referred to as the mucosa), lamina propria (LP), muscularis propria (MP), adventitia (A), and perivesical fat (PF). The mucous membrane lines the intravesical region (IR) of the bladder and includes a three-layered epithelium, collectively referred to as transitional cell epithelium (TCE) or urothelium, and basement membrane (BM). The three layers of the transitional cell epithelium include the basal cell layer, the intermediate cell layer, and the surface cell layer. The basal cell layer can renew the transitional cell epithelium by cell division. New cells can migrate from the basal layer to the surface cell layer, and the surface cell layer can be covered by glycosaminoglycan (GAG) layer (GL). The function of GAG layer is controversial, possibly serving as an osmotic barrier or even an antibacterial coating for transitional cell epithelium. The basement membrane is a single layer of cells that separates transitional cell epithelium from the lamina propria.
Lamina propria (also referred to as the submucosa or suburothelium) is a sheet of extracellular material that may serve as a filtration barrier or supporting structure for the mucous membrane and includes areolar connective tissue and contains blood vessels, nerves, and in some regions, glands. Muscularis propria (also referred to as the detrusor muscle or the muscle layer) may be interlaced with lamina propria and may have three layers of smooth muscle, the inner longitudinal, middle circular, and outer longitudinal muscle.
When the bladder is empty, the mucosa has numerous folds called rugae. The elasticity of rugae and transitional cell epithelium allow the bladder to expand as the bladder fills with fluid. The thickness of the mucosa and muscularis propria can range between approximately 2 to 5 mm when the bladder is full and between approximately 8 to 15 mm when the bladder is empty.
The outer surface of muscularis propria may be lined by adventitia A about the posterior and anterior surface of the bladder or by the serosa about the superior and upper lateral surfaces of the bladder. Perivesical fat (PF) can surround the bladder outside of the serosa or adventitia. In some cases, a variety of fascia layers may surround or support the organs of the pelvis. Collectively, the fascias near the urinary bladder can be referred to as perivesical fascia.
A number of therapies have been developed for treating overactive bladder, including delivery of anticholinergic drugs, bladder retraining, sacral nerve stimulation (SNS), intravesical drug infusions, surgical denervation procedures, surgeries to increase bladder volume (e.g., detrusor myomectomy, augmentation cystoplasty) and botulinum toxin (e.g., Botox®, Dysport®, etc.) injections into the bladder wall. Each of these therapies has drawbacks, as described below.
Anticholinergic drugs, used alone or in combination with traditional nonsurgical approaches, such as bladder retraining, Kegel exercises, biofeedback, etc., often is used as first-line therapy for overactive bladder; however, the mode of action is uncertain. Anticholinergic drug use was initially thought to decrease contractions of the detrusor muscle during the filling stage (e.g., detrusor muscle overactivity, unstable detrusor muscle, etc.). However, it is now believed that anticholinergic drugs may not change detrusor muscle contractility, but instead modulate afferent (e.g., cholinergic) nervous traffic to the central nervous system.
Efficacy of anticholinergic drugs is generally quite modest, as approximately 50% of patients find such therapy subjectively inadequate. A reduction of 10% to 20% in the number of micturations per day (e.g., from 11 micturations to 9 micturations) and a reduction of 50% in urinary incontinence episodes (e.g., from 2 per day to 1 per day) is typical. However, these effects are frequently inadequate to significantly improve patient quality of life (QOL). Many patients would not even notice a change of 2 micturations per day unless they are keeping a log for a formal study. The remaining urinary incontinence episodes, although slightly less in number, continue to maintain the stigma and lifestyle limitations of the disease, such as the inability to travel or to be active, social withdrawal, etc. In addition, anticholinergic drugs can have side effects, including dry mouth, constipation, altered mental status, blurred vision, etc., which may be intolerable, and in many instances outweigh the modest benefits attained. Approximately 50% of patients abandon anticholinergic therapy within 6 months.
Sacral nerve stimulation (SNS) has a higher level of efficacy (e.g., up to 80% in well-selected and screened patients), but here too the mode of action is not well understood. The clinical benefit of SNS for urinary incontinence was a serendipitous finding during clinical trials of SNS for other conditions. The SNS procedure has a number of drawbacks: it is expensive and invasive, and requires surgery for temporary lead placement to test for patient response, followed by permanent lead placement and surgical implantation of a pulse generator in patients who responded favorably to the temporary lead. Regular follow-ups also are required to titrate SNS stimulation parameters, and battery replacements are necessary at regular intervals.
A variety of surgical denervation or disruption procedures have been described in the literature, but most have showed poor efficacy or durability. The Ingelman-Sundberg procedure, first developed in the 1950s and described in Ingelman-Sundberg, A., “Partial denervation of the bladder: a new operation for the treatment of urge incontinence and similar conditions in women,” Acta Obstet Gynecol Scand, 38:487, 1959, involves blunt surgical dissection of the nerves feeding the lateral aspects of the bladder near its base. The nerves are accessed from the anterior vaginal vault, with the dissection extending bilaterally to the lateral aspect of the bladder. The denervation process is accomplished somewhat blindly, using blunt dissection of the space and targeting the terminal pelvic nerve branches. Although capable of producing promising results, the procedure as originally proposed entails all of the drawbacks and expense normally associated with surgical procedures.
McGuire modified the Ingelman-Sundberg procedure in the 1990s, as described in Wan, J., et al., “Ingelman-Sundberg bladder denervation for detrusor instability,” J. Urol., suppl., 145: 358A, abstract 581, 1991, to employ a more limited and central dissection within the serosal layer of the bladder, staying medial to the vaginal formices. Surgical candidates for the Modified Ingelman-Sundberg procedure can be screened to isolate likely “responders” using sub-trigonal anesthetic injections. As reported in 1996 by Cespedes in Cespedes, R. D., et al., “Modified Ingelman-Sundberg Bladder Denervation Procedure For Intractable Urge Incontinence,” J. Urol., 156:1744-1747 (1996), 64% efficacy was observed at mean 15 month follow-up following the procedure. In 2002, Westney reported in Westney, O. L., et al., “Long-Term Results Of Ingelman-Sundberg Denervation Procedure For Urge Incontinence Refractory To Medical Therapy,” J. Urol., 168:1044-1047 (2002), achieving similar efficacy at mean 44 month follow-up after the procedure. More recently, in 2007, Juang reported in Juang, C., et al., “Efficacy Analysis of Trans-obturator Tension-free Vaginal Tape (TVT-O) Plus Modified Ingelman-Sundberg Procedure versus TVT-O Alone in the Treatment of Mixed Urinary Incontinence: A Randomized Study,” E. Urol., 51:1671-1679 (2007), using a combination of a transvaginal tape (TVT) sling (the “gold standard” surgical therapy for stress incontinence) and the Modified Ingelman-Sundberg procedure for mixed incontinence patients and showed a significant benefit for including the Modified Ingelman-Sundberg procedure, over the TVT sling alone, out to 12 months follow-up following the procedure.
Despite its clinical success, however, the Modified Ingelman-Sundberg procedure has not been widely adopted, as it is highly invasive and requires general anesthesia. Further, the terminal nerve branches are not visible to a surgeon, and thus, the dissection must be performed using approximate anatomical landmarks rather than using direct visualization of target nerve branches. Possible complications of the Modified Ingelman-Sundberg procedure include the risks associated with anesthesia, blood loss, vaginal numbness or fibrosis, adhesions, fistulas, vaginal stenosis, wound infection, or dyspareunia (pain with intercourse). Perhaps most importantly, efficacy of the Modified Ingelman-Sundberg procedure may be dependent upon surgical skill and technique.
More recently, another therapy involving injection of botulinum toxin (e.g., Botox®) into the bladder wall has been developed to address the symptoms of overactive bladder by blocking nerve traffic and causing temporary muscle paralysis following injection. During the injection procedure, which may be performed in a physician's office under local anesthesia, a cystoscope is introduced into the bladder through the urethra and a number of separate cannula injections (e.g., 20-30) are made into the bladder wall. Initially the trigone, the area of the bladder defined by the ostia of the two ureters and the urethra, was avoided due to concerns about procedural pain due to dense afferent innervation of the trigone region and the potential for vesicoureteral reflux. However, the trigone region has more recently been included, and sometimes specifically targeted to the exclusion of the dome of the bladder. Initially, botulinum toxin was assumed to act only on the efferent motor nerves (e.g., causing partial paralysis of the detrusor muscle). More recent research indicates that botulinum toxin may have an effect on afferent sensory nerves as well. U.S. Pat. No. 8,029,496 to Versi provides an example of a system for delivering such a therapeutic agent to the trigone of the bladder through the vaginal wall.
Typically, botulinum toxin injections achieve a fairly high level of efficacy (e.g., resolution of symptoms), with maximum changes in cystometric capacity peaking at 4 weeks and complete continence being achieved in about half of patients. However, botulinum toxin does carry with it the risks of systemic effects, such as flu-like symptoms, nausea, weakening of respiratory muscles, transient muscle weakness, allergic reaction, or developed sensitivity. Other adverse events associated with botulinum toxin injections include acute urinary retention (AUR), large postvoid residual volume (PVR), difficulty in urination (“straining”), and urinary tract infection (UTI). Challenges with botulinum toxin therapy include procedural skill (e.g., dexterity with cystoscope and needle), uncontrolled drug diffusion, variable needle penetration depth, and reproducibility of technique. In addition, the effects of botulinum toxin wear off with time, typically after 6-9 months, requiring repeat injections for the lifetime of the patient.
Stress urinary incontinence, typically affecting females, is an anatomic issue where the pelvic floor has been damaged and weakened, such as during childbirth. Here, front line therapies are conservative (e.g., Kegel exercises or biofeedback), and a variety of minimally invasive surgical therapies are available as second line therapies. Examples of these second line therapies include sling procedures, bladder neck suspension, transvaginal tape (TVT), etc. In each, the procedure is a day surgery performed on an outpatient basis. Success rates are high, and the procedures have been embraced by the medical community.
In addition, new therapies have been developed to treat stress urinary incontinence, such as the Renessa system offered by Novasys Medical, Inc., which is used in an office-based procedure. U.S. Pat. No. 6,692,490 to Edwards, assigned to Novasys Medical, discloses the treatment of urinary incontinence and other disorders by the application of energy and drugs.
Finally, a majority of males will develop some degree of urinary obstruction from benign prostate hyperplasia (BPH), or “enlarged prostate”, over their lifetime. Since urinary obstruction is known to be a cause of overactive bladder, bladder symptoms in males are generally presumed to be secondary to the enlarged prostate. However, resolution of the urinary obstruction (e.g., by one of the many variants of transurethral treatments of the prostate) does not resolve the bladder symptoms in about a quarter of the patients. Thus, it would be desirable to offer a minimally invasive therapeutic procedure targeting these remaining patients whose symptoms remain after prostate therapy.
Further, there is a growing preference for “watchful waiting” for prostate disease, even for cases of actual prostate cancer, and many of these patients will develop symptoms of overactive bladder due to the urinary obstruction from their growing prostate. Thus, there is the potential to provide a therapy that targets the bladder symptoms prior to or instead of providing therapy targeting the prostate itself.
Males also may experience idiopathic OAB, that is OAB not secondary to an enlarged prostate or other urinary obstruction, and require a primary therapy for the OAB symptoms.
In view of the foregoing, it would be desirable to provide a minimally invasive procedure for modulating bladder function to treat or resolve overactive bladder and provides durable relief for patients suffering from these debilitating conditions.